Tuesday, December 27, 2005

House Project: Fun With Filters

I went up this morning to try and figure out why the lead filter seems to have cut water pressure to nearly useless. At the suggestion of the vendor, I opened up the filter housing, and verified that yes, the plastic sheeting was not left on the filters. Then I removed all the filters from the housing. This was an unpleasant task, sitting in the garage, while a freezing rain with a mighty wind behind blew in on me. My hands are numb from the cold, and the filters have water from the water tank, which is well above freezing, but still plenty cold. It could have been worse--the heating guy was hooking up the backup generator to the LP gas line, in the rain, standing in cold, sucking mud.

Anyway, I was only able to get 12 of the 14 filters out of the filter housing. These are held in place by big plastic nuts that are are supposed to be "hand tightened only." Perhaps they were, but I do not want a firm handshake from whoever "hand tightened" these nuts. Still, this was enough to demonstrate that the pressure problem was strictly a matter of the filters--not something else failing.

I spent some time discussing the problem with the guy at Filtration Technology who sold us the housing and lead filters. I notice that when I removed the filters, they were gray--not white, like new filters. I also noticed that the water coming out of the faucets is now tinted lightly yellowish-brown.

It turns out that the lead filters are one micron--and apparently, absolute one micron. Nothing larger than one micron gets through--as distinguished from most water filters, which have a nominal filtering size which actually means that most particles of the specified size are stopped. Filtration Technology says that the prefilter was probably not specified tight enough, and what has happened is that fine particulate matter in the several micron size has clogged the lead filters. Their proposed solution is to replace the current prefilter (which I think might be 25 micron or so) with a nominal two micron filter, feeding into a housing with a nominal one micron filter. The two and one micron filters are much cheaper to replace, and will give a much longer life to the lead filters. They are also suggesting that we should have pressure gauges on the input and output of the lead filter housing, so that we can see when it starts to clog.

I have received a few emails asking why I am bothering with lead filters on a new house. The answer is that water tests have shown variously 15 and 37 parts per billion of lead in our water--probably because we are on the edge of a rather impressive granite batholith. Granite often has gold and silver, and where you find silver, you often find lead. Certainly, some parts of northern Idaho have silver and lead in proximity, and so I am assuming that the granite upslope from us is the source of the lead in our ground water.

Last house project entry.

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